1. Field of Invention
This invention relates to correction of phase dispersions created by amplification of related RF signals in two or more traveling wave tube amplifiers.
2. Description of the Prior Art
There are situations, such as in retrodirective arrays, in which two or more phase-related RF signals require amplification. A practical manner of amplifying RF signals is by means of traveling wave tube amplifiers. However, as is known, traveling wave tube amplifiers are very sensitive to power supply fluctuations, temperature changes, and the like; thus, phase differences created within the amplifiers themselves can vary as between two traveling wave tube amplifiers as a function of time, even if the amplifiers are carefully matched. In addition, it is difficult to find traveling wave tube amplifiers which introduce precisely the same phase change of signals amplified therein as a function of supply voltage, temperature and input frequency. This becomes particularly true when three or more traveling wave tube amplifiers are to be utilized for phase-related signals, since the difficulty of achieving a match increases geometrically with the number of amplifiers which must be matched.
A partial solution to the problem can be achieved by sensing the phase differences and comparing any dispersion of the output phase difference between two or more phase-related signals to the input phase difference of such signals, and using this phase dispersion to control the grid voltage of the traveling wave tube amplifier. However, this requires that the phase characteristics of the grid control of the traveling wave tube amplifier be known, and non-erratic. If the grid characteristic is erratic, the correcting loop will apply correction signals for error on every signal pulse received, due to the error caused by the loop itself, in addition to errors caused by power, temperature or frequency changes.